Device for manufacturing electron tubes



Feb. 11, 1969 R. LEGOUX DEVICE FOR MANUFACTURING ELECTRON TUBES Original Filed Feb. 14, 1966 v Sheet I INVENTOR. RENE LEGOUX AGE T Feb. 11, 1969 R. u-zsoux DEVICE FOR MANUFACTURING ELECTRON TUBES Sheet Original Filed Feb. 14, 1966 I INVENTOR. RENE LE GOUX AGENT United States Patent 3,427,088 DEVICE FOR MANUFACTURING ELECTRON TUBES Ren Legoux, Sceaux, France, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Original application Feb. 14, 1966, Ser. No. 527,293, now Patent No. 3,353,889, dated Nov. 21, 1967. Divided and this application June 2, 1967, Ser. No. 659,249

Claims priority, application France, Feb. 23, 1965,

U5. Cl. 316-31 1 Claim Int. Cl. H01j 9/46, 9/26, 9/38 ABSTRACT OF THE DISCLOSURE A device is disclosed for sealing two parts of an evacuated envelope housing a photosensitive layer. One part is provided with a continuous upstanding rim having a groove therein for receiving a corresponding rim portion of the other part. The parts are placed in a vacuum bell which can be exhausted and the parts are held a given distance from each other while a photosensitive layer is applied in vacuo to a supporting body forming part of one of the envelope portions from a vapor deposition furnace.

This application is a division of application Ser. No. 527,293, filed Feb. 14, 1966, now US. Patent No. 3,353,889.

The invention relates to a method of manufacturing an electron tube having a photo-sensitive layer, while in the vacuum space in which the tube parts are degassed at a high temperature the two parts of the tube envelope to be joined are held at a given distance from each other, a photo-sensitive layer is provided and the envelope parts concerned are united to a closed tube by cold pressing, while the vacuum of the vacuum space is obviated and the ready tube is removed. Such a method is known for the manufacture of cascade image intensitying tubes not showing exhaust tube. It is completely carried out in a vacuum space. The tube parts are degassed therein and a photo-sensitive layer of the desired, frequently complex composition is applied by vapor deposition to a supporting body. After the supporting body, thus provided with a sensitive layer, which must not be exposed to the ambient atmosphere, is mounted in one of the envelope parts, the two tube parts are joined to each other (still in vacuo) by pressing the opposite rims with a great force one against the other. The material of these rims is copper.

It has now been found that this method may be employed on a greater scale and can be made suitable particularly for the reproductible manufacture of photoelectric tubes, Vidicon tubes etc. by carrying out the invention, which is characterized in that one of the two envelope parts is provided with an uninterrupted edge, the upwardly orientated side of which is provided with a groove, whereas the other part has a corresponding edge, the downwardly orientated side of which has a profile suitable for cooperation with the first-mentioned edge, while during or after the degassing process for the various tube parts, when the tube parts are remote from each other, a mass introduced into said groove of soft material, preferably indium is melted, after which the parts are moved towards each other and away from each other so that the downwardly orientated edge of one of the tube parts is wetted by dipping in the bath of molten soft material in the .groove of the other part, the parts being then cooled and the photo-sensitive layer being provided between the two parts of the tube envelope and finally the tube being closed by pressing the two envelope parts provided at their edges with a layer of soft material one against the other in the cold state.

It is thus proposed to wet one of the parts by dipping it in a molten bath and to press the two parts with heavy force one against the other in one and the same vacuum space so that an intermolecular connection is established between the rims provided with a layer of soft solder.

It should be noted that it is known per se to introduce a material such as indium between the front plate and the adjacent part of a Vidicon tube and to establish a firm connection by using a compressive force between the two parts, in which case a high temperature is not required. The photo-sensitive layer, which should not be exposed to high temperatures, can then be applied to the front plate before the said parts are united to form a bulb. In this method the parts concerned are not wetted in vacuo and the connection between said parts is not established in vacuo.

It should furthermore be noted that it is also known to provide two parts in vacuo with an indium layer and to join them by cold pressing outside the vacuum space. The indium layer is applied by vapor deposition instead of by dipping in a bath, to the rims of the two parts to be joined. There is not applied :a photo-sensitive layer in this case.

In a preferred embodiment of the method according to the invention the upwardly oriented groove in uninterrupted rim of one of the tube parts has the shape of a V and the corresponding rim of the other tube part has a profile fitting in said groove.

The invention furthermore provides a particular method embodying this invention which is characterized in that in the position in which the tube parts partly covered with a layer of a soft material are remote from each other a number of vapor-deposition sources are arranged temporarily :between said envelope parts and energized so that a supporting body in one of the tube parts can be provided with a photo-sensitive layer, after which said sources are removed from between the tube parts and the tube is sealed.

In contrast to the conventional vapor-deposition techniques, in which the object is provided with a photosensitive layer at a stationary place remote from the tube, after which it is introduced between the tube parts to be united, no stationary furnace but a furnace movable in vacuo is employed in this method, which furnace is temporarily operative between the tube parts. A device suitable for carrying out this method, which comprises a vacuum bell to be exhausted which can be connected with a pump, means for holding the two envelope parts of an electronic tube at a given distance from each other, a furnace having vapor-deposition means for applying a photo-sensitive layer in vacuo to the supporting body which forms part of one of the envelope parts and means for pressing the facing rims of the envelope parts to be united in the cold state, is furthermore characterized in that the means for holding the envelope parts to be united serve to displace these parts with their facing rims only in a direction of height relatively to each other along a set of standing guide columns, and in that the device comprises, furthermore, means for moving the vapor-deposition furnace reciprocatorily in a. lateral direction, which furnace is located in one of its positions at such a place between the envelope parts to be joined that the vapor-deposition means are just located opposite the supporting body to be covered.

The invention will be briefly described with reference to the drawing, in which FIG. 1 is a side elevation of a pump and partly a sectional view of a vacuum bell inside which a photoelectric tube is manufactured.

FIGS. 2a and 2b are a longitudinal sectional and a cross-sectional view respectively of part of a vacuum bell inside which a photo-intensifying tube is manufactured and FIG. 3 shows the relatively co-operating closing rims of the two parts to be united of the envelope of an electronic tube.

The electronic tube to be manufactured by the method according to the invention is arranged in vacuum space, the lower part of which has a body 1 of stainless steel, on which a glass bell is mounted. All members holding the various parts of the electronic tube and the members for moving said parts of various mechanisms to be moved in the vacuum space are connected with said body.

The vacuum in the bell 2 is obtained by means of a pump 5, which communicates through a metal valve 6 with the body 1. The various parts are intercoupled by suitable metal connections so that the vacuum exhibits a pressure of 1O torr.

The envelope of the electronic tube is formed by two cylindrical portions each having a metal ring 9 and 10 respectively, the facing rims of which rings are pressed one against the other under the action of a compressive force so that the envelope of the tube is sealed (see FIG. 3). The connection is established by pressing two parts against each other, which are covered with the same material, the yielding properties of which are favorable. Use is made of asoft metal. Among the suitable materials indium, tin, lead, preferably indium is chosen. This metal is introduced into a V-shaped groove 9a of the lowermost part 9.

The downwardly oriented rim 10a of the uppermost part 10 is coated with the soft material by dipping this rim in a metal bath obtained by melting the material in the groove 9a. The parts 9a and 10a are previously cleaned preferably by etching and they may be coated with a gold layer of 1 to 2 1. thick.

The parts of the electronic tube to be manufactured are arranged inside the hell 2. The part forming the supporting body 11 of the photocathode is immovably held in the part 3, which part is supported from two columns 12. The associated envelope part 13 of the electronic tube is secured to a block 14, which is displaceable along the columns 12. This block 14 is coupled with a rod 4 of a hydraulic press, which can provide a force of a few tons. The passage of the rod 4 through the wall of the vacuum space is of the conventional type so that a further descrip tion may be dispensed with.

The members containing the sources of the basic materials for the formation of the photo-sensitive layers(s) (for example Ag, Sb, Na, K, Rb, Cs) are also arranged inside the glass bell 2. These members are arranged preferably in a single group on a rotatable arm 18. They are located in an auxiliary space 15 serving temporarily as a vapor-deposition furnace. These members are simultaneously displaced by turning the arm 18. This arm is coupled by means of a lever and bellows system so that, when it is moved, the vacuum is maintained in the bell 2. Just before the formation of the photosensitive layer, the sources are arranged opposite the supporting body 11 to be coated and removed therefrom as soon as this layer is formed.

For this purpose the block 14 has first to be moved downwards so that the vapor-deposition device with the electrodes 19 is situated opposite the supporting body 11 for the sensitive layer.

When all members and the vapor-deposition furnace are arranged inside the glass bell 2, the bell is sealed in a vacuum-tight manner and the vacuum is produced inside the bell. Then thermal degassing is performed for the bell 2 itself, the various pump parts and all components of the electronic tube to be manufactured.

The vapor-deposition sources for the photo-sensitive layer are degassed at a temperature between 600 and 700 C. by heating with Joules heat. Also the indium in the groove 9a is then melted.

At the termination of the degassing process at a high temperature the block 14 is moved upwardly until the rim 10a is dipped in the molten indium bath in the groove 9a. The soft metal covers the metal rim 10a within a few minutes. Then the parts are moved away from each other and the temperature of the assembly is reduced to room temperature, the indium thus hardening.

The auxiliary space 15 with the various vapor-deposition sources is then moved in between the spaced envelope parts 9 and 10 by actuating the arm 18 so that the supporting body 11 forms the upper boundary of the auxiliary space 15; an opening of a few millimeters should, however, be left in the auxiliary space for pumping away unwanted gases developed by the various sources.

The materials which have to be evaporated at room temperature are first evaporated. Then the bell 2 and the tube parts are heated at a temperature which depends upon the nature of the photosensitive layer and may reach 250 C. This rise in temperature may be obtained by energizing a heating element 16.

After the termination of the physical-chemical formation of the photo-electric layer the temperature of the assembly is reduced to the ambient temperature of 30 to 40 C. This reduction may be accelerated by having a cooling liquid circulating through a cooling pipe 17 inside the bell 2.

Finally the photo-electric tube is sealed. For this purpose first the auxiliary space 15 with the sources is tilted away into the position indicated in broken lines in FIG. 2b. Then the block 14 is moved upwardly by means of the rod 4 of the hydraulic press. The force exerted is of the order of 10 kgs/mm. of the circumference of the rim (9, 10) and ensures a firm interconnection of the metallic, indium-coated surfaces.

Then the vacuum of the bell 2 may be obviated and the ready tube may be removed.

FIGS. 2a and 2b related to the method described above for the manufacture of .a photo-intensifying tube and corresponding parts are designated by the same reference numerals. FIG. 2b shows the members for tilting away the auxiliary space 15 into the position shown in broken lines. FIG. 2a indicates by arrows the direction of vapordeposition of one of the photo-sensitive materials (Sb). The electrodes for the diffuse distribution of alkali metals (Na, K, Rb) are designated by 19.

What is claimed is:

1. A device for manufacturing an electron discharge tube having an evacuated envelope housing a photosensitive layer, said envelope comprising two parts one of which is provided with a continuous rim having an upwardly orientated side provided with a groove and the other part having a corresponding rim with a mating profiled portion, the portions being joined by soft meltable material supplied from a plurality of externally positioned vapor-deposition sources of said material comprising a vacuum bell to be exhausted, means to connect said vacuum bell with a pump, means for holding the two envelope parts of the electronic tube at a given distance from each other, a furnace having vapor deposition means for applying a photo-sensitive layer in vacuo to a supporting body, which forms part of one of the envelope portions, and means for pressing the facing rims of the envelope portions to be united in the cold state, said means for holding the envelope portions to be united serving to displace these portions with their facing rims only in a direction of height relatively to each other along a set of standing guide columns, said device further comprising means for moving the vapor-deposition furnace reciprocatorily in a lateral direction, which furnace is References Cited UNITED STATES PATENTS 9/1959 Terry et al -c 3l63l RICHARD H. EANES, JR. Primary Examiner. 

